• Steel and Composite Structures
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• v.31 no.2
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• pp.125-131
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• 2019

This paper presents the results of an experimental study to investigate the mechanical behavior of partially encased composite columns confined by CFRP under axial compression. The results show that the failure of the partially encased composite columns confined by CFRP occurred due to rupture of the CFRP followed by local buckling of the steel flanges. External wrapping of CFRP effectively delayed the local buckling of the steel flanges. The load carrying capacity of the column increased with the application of CFRP sheet. And the enhancement effect of the column was increased with the number of CFRP layer.

• Magazine of the Korea Concrete Institute
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• v.10 no.6
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• pp.241-252
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• 1998

The objective of the research stated herein is to observe the actual responses of a low-rise nonseismic moment-resisting reinforced concrete frame subjected to varied levels of earthquake ground motions. First, the reduction scale for the model was determined as 1 : 5 considering the capacity of the shaking table to be used and the model was manufactured according to the similitude law. This model was, then, subjected to the shaking table motions simulating Taft N21E component earthquake ground motions, whose peak ground accelations (PGAs) were modified to 0.12g, 0.2g, 0.3g, and 0.4g. The lateral accelerations and displacements at each story and local deformations at the critical reginos of the structure were measured. The base shear was measured by using self-made load cells. Before and after each earthquake simulation test, free vibration tests were performed to find the change in the natural period and damping ratio of the model. The test data on the global and local behaviors are interpreted. The model showed the linear elastic behavior under the Taft N21E motion with the PGA if 0.12g, which represents the design earthquake in Korea. The maximum base shear was 1.8tf, approximately 4.7 times the design base shear. The model revealed fairly good resistance to the higher level of earthquake simulation tests. The main components of its resistance to the high level of earthquakes appeared to be 1) the high overstrength, 2) the elongation of the fundamental period, and 3) the minor energy dissipation by inelastic deformations. The drifts of the model under these tests were approximately within the allowable limit.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.2
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• pp.34-45
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• 2017

Cyclic loading tests for a total of nine test specimens were performed to evaluate the seismic performance of the exposed steel column-base plate connections. From the tests, flexural strength, deformation capacity, energy dissipation, and initial stiffness were investigated. The primary test parameters were the thickness of base-plate, embedment length of anchor bolt, the presence of hook, and rib plates. Test results showed that flexural behavior of column base-plate connection was substantially affected by the base-plate thickness, embedment length and the number of anchor bolts. On the other hand, the effect of rib plates on the increase of the flexural performance was not observed. The initial stiffness of the test specimens was about 15% of the flexural stiffness obtained by assuming that the support is fixed. As a result, even if the exposed column base-plate is designed in accordance with current design recommendations, in case that bond strength between concrete and the anchor bolts is not sufficient, the base-plate connection showed an unaccceptable load-displacement behavior.

• Magazine of the Korean Society of Agricultural Engineers
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• v.32 no.3
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• pp.39-46
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• 1990

This paper was analized the thermal conductivity of polystylene (TENSAR- GEOGRID) embeding into the subbase through frost penetration depth, frost heave, change of bearing capacity, and soil moisture movement due to freezing, thawing and icing actions, and their results were as follows : 1.The change of temperature into the sub-base was much increased by the Tensar-Geogrid insertion, and the frost penetration and frost heave were decreased as the thinner of the insulation thickness but the thawing velocity of melting period was appeared to be faster in case of non-insulated. 2.The frost heave had a close relationship with the thickness of insulations which was reasonably included anti-frost effects. 3.The moisture content during the freezing period of upper layer of the insulation insertion was increased by 15 per cent but it was returned to initial state of the thawing period, and at the down layer temporarily increased by 10 per cent and returned to the original state at once. 4.The insulation was acted as a function of distribution of surcharge, and the settlement of the sub-base was about 1.5 mm under 15 tonnage of load and which was included within the allowable limits. 5.The sliding resistance due to the icing which was induced by the insulation insertion into the sub-base was appeared as more 40 per cent than noninsulation area, so that the insulations should be restricted on the place such as mountains, curved and cross area which were required the braking power under the traffics.

• Steel and Composite Structures
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• v.23 no.2
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• pp.195-204
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• 2017

The effects of plaster on the behavior of single-story single-bay masonry-infilled steel frames under in-plane base accelerations have been experimentally investigated by a shake-table. Tested structures were made in a 1/3 scale, with realistic material properties and construction methods. Steel frames with high and low flexural rigidity of beams and columns were considered. Each type of frame was tested with three variants of masonry: (i) non-plastered masonry; (ii) masonry infill with conventional plaster on both sides; and (iii) masonry infill with a polyvinyl chloride (PVC) net reinforced plaster on both sides. Masonry bricks were made of lightweight cellular concrete. Each frame was firstly successively exposed to horizontal base accelerations of an artificial accelerogram, and afterwards, to horizontal base accelerations of a real earthquake. Characteristic displacements, strains and cracks in the masonry were established for each applied excitation. It has been concluded that plaster strengthens the infill and prevents damages in it, which results in more favorable behavior and increased bearing capacity of plastered masonry-infilled frames compared to non-plastered masonry-infilled frames. The load-bearing contribution of the adopted PVC net in the plaster was not noticeable for the tested specimens, probably due to relative small cross section area of fibers in the net. Behavior of masonry-infilled steel frames significantly depends on frame stiffness. Strong frames have smaller displacements than weak frames, which reduces deformations and damages of an infill.

• Journal of the Korean Geotechnical Society
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• v.34 no.7
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• pp.39-49
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• 2018

Jacked pile that involves the use of hydraulic jacks to press the piles into the ground is free from noise and vibration, and is possibly installed within a limited construction area. Thus, as an alternative to conventional pile driving methods, pile jacking could become widely accepted for the construction projects in urban area (e.g., reconstruction or remodeling construction projects). Great concern has arisen over the prediction of axially loaded jacked pile behavior. Against this background, a series of pile load tests were hence conducted on a jacked steel pipe pile installed in weathered zone (i.e., weathered soil and weathered rock). From the test results, base resistance and shaft resistance for each test condition were evaluated and compared with the values predicted by the previous driven pile resistance assessment method. Test results showed that the previous driven pile resistance assessment method highly underestimated both the base and shaft resistances of a jacked pile; differences were more obviously observed with the shaft resistance. The reason for this discrepancy is that a driven pile normally experiences a larger number of loading/unloading cycles during installation, and therefore shows significantly degraded stiffness of surrounding soil. Based on the results of the pile load tests, particular attention was given to the modification of the previous driven pile resistance assessment method for investigating the axially loaded jacked pile behavior.

• Journal of the Korean GEO-environmental Society
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• v.14 no.8
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• pp.53-60
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• 2013

The compaction control method of national road substructure is using field density test to determine the relative compaction and plate bearing test to check the load bearing capacity. However, these two tests digitize a construction site manager's judgment based on his experience, so mechanical basis is weak. Resilient modulus method, which is recently being used to resolve such problem, is evaluated as a rational design method of pavement structure that can rationally reflect the stress-strain state of pavement materials that is caused by the condition of load repetition of vehicle load. However, the method of measuring the resilient modulus is difficult and lengthy, and it has many problems. To replace it, light falling weight test is recently being proposed as a simple test method. Therefore, this research uses dynamic plate loading test, which quickly and simply measures the elastic modulus of the subgrade and sub-base construction and site of maintenance, to judge the possibility of compaction control of the stratum under the road, and it proposes relation formula by analyzing the result of static load test.

• Journal of the Korean Geosynthetics Society
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• v.8 no.2
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• pp.55-62
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• 2009

Recently, new development projects are being carried out with the soft ground located along the West coast and the South coast. As soft grounds have complex engineering properties that the load bearing capacity is low and high compressibility, it needs to solve this problems Prior to structures are constructed by the method of improvement of soft ground. The sand mat is usually being used for improvement of soft ground as a horizontal drain material and loading base. But, as the volume is enormous and an amount of demanded sand is increased, it is state of short in supply. This paper presents the feasibility study to use of precious slag ball instead of sand mat as the replacing material through the basic soil property tests, the medium of discharge capacity test and analysis of settlement character.

• Journal of Digital Contents Society
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• v.2 no.1
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• pp.73-79
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• 2001

Most of the existing algorithms try to disseminate the multimedia contents of internet service provider(ISP), without taking into account the needs and characteristics of specific websites including e-learning systems with web-based .educational contents. Sometimes the client must select the best one among the replicated repositories. However, this is a less reliable approach because clients' selections are made without prior information on server load capacity. In this paper we propose an agent system inspired by the need of improving QoS of delivering web-based educational multimedia contents without incurring long access delays. This agent system consists of three components, Analyzer, Knowledge Base, and Automaton embedded the capacity algorithm. It analyzes and investigates traffic information collected from individual replicated server by learners' requests, and selects a server which is available and is expected to provide the fastest latency time and the lowest loaded capacity, and achieves high performance by dynamic replicating web resources among multiple repositories.

• Structural Engineering and Mechanics
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• v.61 no.2
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• pp.245-253
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• 2017

The increasing lack of good quality soils allowing the development of roadway, motorway, or railway networks, as well as large scale industrial facilities, necessitates the use of reinforcement techniques. Their aim is the improvement of the global performance of compressible soils, both in terms of settlement reduction and increase of the load bearing capacity. Among the various available techniques, the improvement of soils by incorporating vertical stiff piles appears to be a particularly appropriate solution, since it is easy to implement and does not require any substitution of significant soft soil volumes. The technique consists in driving a group of regularly spaced piles through a soft soil layer down to an underlying competent substratum. The surface load being thus transferred to this substratum by means of those reinforcing piles, which illustrates the case of a piled embankment. The differential settlements at the base of the embankment between the soft soil and the stiff piles lead to an "arching effect" in the embankment due to shearing mechanisms. This effect, which can be accentuated by the use of large pile caps, allows partial load transfer onto the pile, as well as surface settlement reduction, thus ensuring that the surface structure works properly. A technique for producing rigid piles has been developed to achieve in a single operation a rigid circular pile associated with a cone shaped head reversed on the place of a rigid circular pile. This technique has been used with success in a pile-supported road near Bourgoin-Jallieu (France). In this article, a numerical study based on this real case is proposed to highlight the functioning mode of this new technique in the case of industrial slabs.